Shock-absorbing damping rubber EVA (Ethylene Vinyl Acetate) foaming material and preparation method thereof

Abstract

The invention relates to the technical field of EVA foam materials, in particular to a shock-absorbing damping rubber EVA foam material and a preparation method thereof, the shock-absorbing damping rubber EVA foam material comprises the following raw materials by weight: 100 parts of ethylene-vinyl acetate resin, 10-15 parts of a damping material of SiO2 aerogel modified lignin, and 2-4 parts of a foaming agent AC; the preparation process of the damping material comprises the following steps: preparing silane coupling agent modified silicon dioxide aerogel; adding lignin into ethanol, stirring for 30 minutes, then adding the silane coupling agent modified silicon dioxide aerogel, and reacting for 12 hours at the temperature of 65 DEG C to obtain a damping material of the SiO2 aerogel modified lignin; silicon dioxide aerogel and lignin are bridged through a silane coupling agent, and a core-shell structure damping unit is constructed. According to a core layer, the silicon dioxide aerogel provides a nano-porous interface, and friction energy consumption is increased; and in the shell layer, lignin is chemically bonded with aerogel through silane bonds to form a deformable dissipative phase.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of EVA foaming materials, in particular to a shock-absorbing damping rubber EVA foaming material and a preparation method thereof. BACKGROUND

[0002] Ethylene-vinyl acetate copolymer (EVA) foaming materials are widely used in shoe materials, sports equipment packaging, building shock absorption and other fields due to their light weight, flexibility and excellent processing performance. However, the traditional EVA foaming materials have the following inherent defects: Insufficient damping performance: the EVA molecular chain segment has a low energy barrier, and the energy dissipation capacity is limited under dynamic load, resulting in an unsatisfactory shock absorption and noise reduction effect, which is difficult to meet the impact absorption requirements of high-precision equipment protection or sports equipment.

[0003] Mechanical strength and lightweight conflict: in order to improve the damping performance, inorganic fillers (such as calcium carbonate and talc) or rubber phases are often added for modification, but such methods significantly increase the material density and easily cause the collapse of the pore structure, resulting in a decrease in resilience and a shortening of the fatigue life.

[0004] Filler dispersion and interface compatibility problems: Nanofillers (such as silicon dioxide and carbon black) are easy to agglomerate and become stress concentration points in the foaming process, inducing the merging and rupture of the pores; Although biomass fillers (such as lignin) have damping potential, they have poor surface hydrophobicity and compatibility with the EVA matrix, and need to be treated with a high dose of coupling agent, which inhibits the foaming efficiency. SUMMARY

[0005] The purpose of the present application is to provide a shock-absorbing damping rubber EVA foaming material and a preparation method thereof. By bridging the silica aerogel and lignin with a silane coupling agent, a "core-shell" structure damping unit is constructed: the core layer: the silica aerogel provides a nano-porous interface to increase the friction energy consumption; the shell layer: the lignin is chemically bonded to the aerogel through a silane bond to form a deformable dissipation phase; synergistic effect: the aerogel nanopores anchor the lignin molecular chains to inhibit agglomeration; the polar groups of the lignin form a hydrogen bond network with the ester groups of the EVA to enhance the interface stress transfer efficiency.

[0006] The purpose of the present application can be achieved by the following technical solutions: A shock-absorbing damping rubber EVA foaming material, comprising the following raw materials by weight: 100 parts of ethylene-vinyl acetate resin, 10-15 parts of SiO2 aerogel modified lignin damping material, and 2-4 parts of foaming agent AC; The preparation process of the SiO2 aerogel modified lignin damping material comprises the following steps: S1: preparing silane coupling agent modified silica aerogel; S2: adding lignin into ethanol and stirring for 30 min, then adding the silane coupling agent modified silica aerogel, and reacting for 12 h at a temperature of 65℃ to obtain the damping material of the SiO2 aerogel modified lignin.

[0007] As a further scheme of the present application: the preparation process of the silane coupling agent modified silica aerogel is as follows: The silica aerogel is placed in dichloromethane to form a suspension, and then the silane coupling agent KH560 is added to the suspension, and stirred and reacted for 6 h to obtain the silane coupling agent modified silica aerogel.

[0008] As a further scheme of the present application: the mass ratio of the silica aerogel, the silane coupling agent KH560 and dichloromethane is 5.0:2.5-3.0:230-270.

[0009] As a further scheme of the present application: the particle size D50 of the modified silica aerogel is controlled at 1-2 microns.

[0010] As a further scheme of the present application: the mass ratio of the lignin, the silane coupling agent modified silica aerogel and ethanol is 70:50:800-1000.

[0011] As a further scheme of the present application: the preparation process of the silica aerogel is as follows: The methyltrimethoxysilane and the methanol are mixed and stirred, and then the oxalic acid solution is added dropwise, and fully stirred at 30℃ for 2 h; then the N,N-dimethylformamide is added dropwise, and the ammonia water solution is added dropwise to adjust the pH value to 8, and stirred for 10 min, and reacted at a temperature of 40℃ for 9 h to obtain the gel; The gel is aged at 50℃ for 24 h, and then the isopropyl alcohol and the n-hexane are added for solvent replacement, each for 1-2 h, and finally washed twice with the n-hexane; and dried at 60℃ for 12 h to obtain the silica aerogel.

[0012] As a further scheme of the present application: the molar ratio of the methyltrimethoxysilane, the oxalic acid and the methanol is 1:0.00016:22-26.

[0013] As a further scheme of the present application: the volume ratio of the methyltrimethoxysilane and the N,N-dimethylformamide is 100:50.

[0014] A preparation method of a shock-absorbing damping rubber EVA foaming material, the method comprising: After the ethylene-vinyl acetate resin, the SiO2 aerogel modified lignin damping material and the foaming agent AC are uniformly mixed according to the above weight ratio, they are placed in an extruder for mixing, and the materials are pressed into a sheet; The sheet is placed on a flat vulcanizer to obtain a shock-absorbing and damping modified EVA material.

[0015] As a further solution of the present invention: the parameters of the flat vulcanizing press are 10 MPa, 170° C., and molding and foaming for 6 minutes.

[0016] Beneficial effects of the present invention: This invention modifies silica aerogel with a silane coupling agent and then reacts it with lignin to produce a SiO2 aerogel-modified lignin damping material. Lignin's vibration damping mechanism primarily relies on its inherent elasticity and shock resistance. Lignin has a high natural frequency and damping ratio, quickly dissipating external impact forces, thereby reducing the transmission and impact of vibration. Furthermore, lignin has excellent energy absorption, converting energy into internal deformation and heat, thereby mitigating the impact of vibration. Therefore, using lignin as a bio-based damping agent in EVA foam materials offers environmentally friendly vibration damping properties. Furthermore, the aromatic rings and double bonds in lignin's molecular structure absorb ultraviolet light, mitigating its damage and decomposition. Furthermore, the aromatic groups in lignin can neutralize free radicals caused by UV light through free radical neutralization reactions, effectively improving the anti-aging and UV resistance of the EVA foam material and mitigating the aging of EVA foams susceptible to long-term exposure to UV (sunlight) and oxygen. The surface will turn yellow and the shock absorption and damping performance will be significantly reduced; SiO2 aerogel has good shock absorption performance due to its special structure and looseness. In the case of movement or vibration, the aerogel can quickly absorb the impact force caused by the vibration and disperse it into the interior of the material, thereby reducing the transmission of vibration. As a result, the SiO2 aerogel and lignin work together to achieve a good shock-resistant effect. The introduction of methyl groups into the SiO2 aerogel of the present invention reduces the density of interconnected gel networks. Due to the presence of steric hindrance, repulsive forces are generated between adjacent methyl groups, making the aerogel exhibit better elasticity, thereby further improving the shock absorption and damping properties of the EVA foam material. Furthermore, the methyl group in the SiO2 aerogel of the present invention is a non-polar group. The introduction of the methyl group can improve the hydrophobicity of the aerogel, making the SiO2 aerogel have excellent hydrophobic properties. Therefore, the introduction of the SiO2 aerogel of the present invention will effectively improve the hydrophobicity of lignin, solving the problems of decreased damping performance and poor dimensional stability of lignin in the wet state. Therefore, the SiO2 aerogel modified lignin as the damping material in the application can significantly improve the energy dissipation efficiency through the synergistic effect of the porous aerogel structure and the lignin molecular chain. The nano-pores of the aerogel can effectively absorb the impact stress wave, and the viscoelasticity of the lignin molecular chain provides a multiple energy conversion mechanism, so that the composite material has excellent shock absorption and noise reduction capability in a wide frequency range (especially high frequency vibration).

[0017] The low density of the SiO2 aerogel greatly reduces the overall weight of the material, and the three-dimensional network skeleton of the SiO2 aerogel and the rigid structure of the lignin form a reinforcing phase, effectively improving the compressive strength and resilience of the foamed material, overcoming the defects of the mechanical properties of traditional lightweight materials. The nano-porous structure of the SiO2 aerogel inhibits air convection, giving the material excellent thermal insulation properties, ensuring that the damping performance remains stable in an environment of-40℃ to 80℃, and is suitable for scenes with large temperature differences such as automobiles and buildings. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application. Embodiment 1

[0019] The shock-absorbing damping EVA foamed material provided by the embodiment of the present application comprises the following raw materials by weight: 100 parts of ethylene-vinyl acetate resin, 10 parts of SiO2 aerogel modified lignin damping material, and 2 parts of foaming agent AC; The preparation process of the SiO2 aerogel modified lignin damping material comprises the following steps: S1: preparing silane coupling agent modified silica aerogel; Specifically, the silica aerogel is placed in dichloromethane to form a suspension, and then silane coupling agent KH560 is added to the suspension, and stirred and reacted for 6 hours. The solvent is vacuumed and dried, and then ground and dispersed to obtain the silane coupling agent modified silica aerogel; The mass ratio of the silica aerogel, the silane coupling agent KH560 and the dichloromethane is 5.0:2.5:230; The particle size D50 of the modified silica aerogel is controlled at 1 microns; S2: lignin is added to ethanol and stirred for 30 minutes, and then the silane coupling agent modified silica aerogel is added, and reacted at a temperature of 65℃ for 12 hours to obtain the SiO2 aerogel modified lignin damping material; The mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:800; More specifically, the silica aerogel preparation process is as follows: Methyltrimethoxysilane (MTMS) and methanol were mixed and stirred, and then oxalic acid solution (0.01 mol / L) was added dropwise and stirred at 30°C for 2 hours. N,N-dimethylformamide was then added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8. The mixture was stirred for 10 minutes and reacted at 40°C for 9 hours to obtain a gel. The gel was aged at 50°C for 24 hours, and solvent replacement was performed by adding isopropanol and n-hexane, respectively, for 1-2 hours each time, and finally washed twice with n-hexane; and dried at 60°C for 12 hours to obtain silica aerogel; The molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:22; The volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:50.

[0020] An embodiment of the present invention also provides a method for preparing a shock-absorbing and damping rubber EVA foam material, comprising the following steps: Step 1: Ethylene-vinyl acetate resin, SiO2 aerogel-modified lignin damping material and foaming agent AC are mixed uniformly according to the above weight ratio, placed in a preheated extruder, and extruded and kneaded under the conditions of each zone temperature of 105°C and a speed of 20 rpm; quickly transferred to an open mill and kneaded for 10 minutes, and then pressed into sheets; The sheet was placed in a preheated flat vulcanizing machine cavity and foamed under 10 MPa and 170°C for 6 minutes to obtain a shock-absorbing and damping modified EVA material. Example 2

[0021] An embodiment of the present invention provides a shock-absorbing and damping rubber EVA foam material, comprising the following raw materials in parts by weight: 100 parts of ethylene-vinyl acetate resin, 12 parts of SiO2 aerogel-modified lignin damping material, and 3 parts of foaming agent AC; The preparation process of the SiO2 aerogel-modified lignin damping material comprises the following steps: S1: Preparation of silane coupling agent modified silica aerogel; Specifically, silica aerogel is placed in dichloromethane to form a suspension, and then a silane coupling agent KH560 is added to the suspension, stirred and reacted for 6 hours, the solvent is vacuum-evacuated, and the suspension is ground and dispersed to obtain a silane coupling agent-modified silica aerogel; The mass ratio of silica aerogel, silane coupling agent KH560 and dichloromethane is 5.0:2.8:250; The particle size D50 of the modified silica aerogel is controlled at 1 micron; S2: Add lignin to ethanol and stir for 30 minutes, then add silane coupling agent modified silica aerogel, and react at 65 ° C for 12 hours to obtain SiO2 aerogel modified lignin damping material; The mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:9000; More specifically, the silica aerogel preparation process is as follows: Methyltrimethoxysilane (MTMS) and methanol were mixed and stirred, and then oxalic acid solution (0.01 mol / L) was added dropwise and stirred at 30°C for 2 hours. N,N-dimethylformamide was then added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8. The mixture was stirred for 10 minutes and reacted at 40°C for 9 hours to obtain a gel. The gel was aged at 50°C for 24 hours, and solvent replacement was performed by adding isopropanol and n-hexane, respectively, for 1-2 hours each time, and finally washed twice with n-hexane; and dried at 60°C for 12 hours to obtain silica aerogel; The molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:24; The volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:50.

[0022] An embodiment of the present invention also provides a method for preparing a shock-absorbing and damping rubber EVA foam material, comprising the following steps: Step 1: Ethylene-vinyl acetate resin, SiO2 aerogel-modified lignin damping material and foaming agent AC are mixed uniformly according to the above weight ratio, placed in a preheated extruder, and extruded and kneaded under the conditions of each zone temperature of 110°C and a speed of 20 rpm; quickly transferred to an open mill and kneaded for 15 minutes, and then pressed into sheets; The sheet was placed in a preheated flat vulcanizing machine cavity and foamed under 10 MPa and 170°C for 6 minutes to obtain a shock-absorbing and damping modified EVA material. Example 3

[0023] An embodiment of the present invention provides a shock-absorbing and damping rubber EVA foam material, comprising the following raw materials in parts by weight: 100 parts of ethylene-vinyl acetate resin, 15 parts of SiO2 aerogel-modified lignin damping material, and 4 parts of foaming agent AC; The preparation process of the SiO2 aerogel-modified lignin damping material comprises the following steps: S1: Preparation of silane coupling agent modified silica aerogel; Specifically, the silica aerogel is placed in dichloromethane to form a suspension, and then the silane coupling agent KH560 is added to the suspension, and stirred for 6 hours, the solvent is vacuumed, and the silica aerogel modified by the silane coupling agent is obtained by grinding and dispersing. The mass ratio of the silica aerogel, the silane coupling agent KH560 and the dichloromethane is 5.0:3.0:270. The particle size D50 of the modified silica aerogel is controlled to be 2 microns. S2: The lignin is stirred in ethanol for 30 minutes, and then the silica aerogel modified by the silane coupling agent is added, and reacted at a temperature of 65 DEG C for 12 hours to obtain the damping material of the lignin modified by the SiO2 aerogel. The mass ratio of the lignin, the silica aerogel modified by the silane coupling agent and the ethanol is 70:50:1000. More specifically, the preparation process of the silica aerogel is as follows: The methyltrimethoxysilane (MTMS) and the methanol are mixed and stirred, and then the oxalic acid solution (0.01 mol / L) is added dropwise, and stirred at 30 DEG C for 2 hours; then the N,N-dimethylformamide is added dropwise, and then the ammonia solution is added dropwise to adjust the pH to 8, and stirred for 10 minutes, and reacted at a temperature of 40 DEG C for 9 hours to obtain a gel. The gel is aged at 50 DEG C for 24 hours, and then the isopropyl alcohol and the n-hexane are added for solvent replacement, each time for 1-2 hours, and finally washed twice with the n-hexane; and dried at 60 DEG C for 12 hours to obtain the silica aerogel. The molar ratio of the methyltrimethoxysilane, the oxalic acid and the methanol is 1:0.00016:26. The volume ratio of the methyltrimethoxysilane and the N,N-dimethylformamide is 100:50.

[0024] The application also provides a preparation method of the shock absorption damping EVA foamed material. The ethylene-vinyl acetate resin, the damping material of the lignin modified by the SiO2 aerogel and the foaming agent AC are mixed uniformly according to the above weight ratio, and then placed in a preheated extruder, and extruded and mixed under the conditions that the temperature of each zone is 115 DEG C and the rotating speed is 20 rpm; and then quickly transferred to an open mill for mixing for 20 minutes, and then the material is pressed into a sheet; The sheet is placed in a preheated flat vulcanizing machine mold cavity, and molded and foamed at 10 MPa and 170 DEG C for 6 minutes to obtain the shock absorption damping modified EVA material.

[0025] Comparative Example 1 Comparative Example 1 is different from Example 1 in that the damping material of the lignin modified by the SiO2 aerogel is not added, and the shock absorption damping modified EVA material is prepared. Performance testing: The damping performance of the shock-absorbing and damping modified EVA materials of Examples 1-3 and Comparative Example 1 was tested, and the test data are shown in the following table: Test method: Dynamic Mechanical Analysis (DMA) Test parameters: Temperature range: -40℃-80℃; Frequency: 1 Hz; strain: 0.1%; Test indicators: Loss factor (tanδ): characterizes the material's shock absorption ability (the higher the peak value, the better the damping performance); tanδ peak Example 1 0.35 Example 2 0.33 Example 3 0.34 Comparative Example 1 0.22 As can be seen from the above table, the damping material of SiO2 aerogel-modified lignin is added to the EVA foam material in the present invention, which will effectively improve the shock absorption and damping performance of the EVA foam material.

[0026] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A shock-absorbing and damping rubber EVA foam material, characterized in that: It includes the following raw materials in parts by weight: 100 parts of ethylene-vinyl acetate resin, 10-15 parts of SiO2 aerogel-modified lignin damping material, 2-4 parts of foaming agent AC; The preparation process of the SiO2 aerogel-modified lignin damping material comprises the following steps: S1: Preparation of silane coupling agent modified silica aerogel; S2: Add lignin to ethanol and stir for 30 minutes, then add silane coupling agent modified silica aerogel, and react at a temperature of 65°C for 12 hours to obtain a damping material of SiO2 aerogel modified lignin.

2. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that: The preparation process of silane coupling agent modified silica aerogel is as follows: The silica aerogel was placed in dichloromethane to form a suspension, and then a silane coupling agent KH560 was added to the suspension, and the mixture was stirred and reacted for 6 hours to obtain a silane coupling agent-modified silica aerogel.

3. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that: The mass ratio of silica aerogel, silane coupling agent KH560 and dichloromethane is 5.0:2.5-3.0:230-270.

4. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that: The particle size D50 of the modified silica aerogel is controlled at 1-2 microns.

5. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that: The mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:800-1000.

6. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that: The preparation process of silica aerogel is as follows: Methyltrimethoxysilane and methanol were mixed and stirred, and then oxalic acid solution was added dropwise and stirred at 30°C for 2 hours; N,N-dimethylformamide was then added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8, stirred for 10 minutes, and reacted at 40°C for 9 hours to obtain a gel; The gel was aged at 50° C. for 24 h, and solvent replacement was performed by adding isopropanol and n-hexane, respectively, for 1-2 h each time, and finally washed twice with n-hexane; and dried at 60° C. for 12 h to obtain silica aerogel.

7. The shock-absorbing and damping rubber EVA foam material according to claim 6, characterized in that: The molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:22-26.

8. The shock-absorbing and damping rubber EVA foam material according to claim 7, characterized in that: The volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:

50.

9. A method for preparing a shock-absorbing and damping rubber EVA foam material, characterized in that: The method is used to prepare the EVA foam material according to any one of claims 1 to 8, and the method comprises: Ethylene-vinyl acetate resin, SiO2 aerogel-modified lignin damping material and foaming agent AC are mixed uniformly according to the above weight ratio, placed in an extruder for mixing, and the material is pressed into a sheet; The sheet is placed on a flat vulcanizer to obtain a shock-absorbing and damping modified EVA material.

10. The shock-absorbing and damping rubber EVA foam material according to claim 9, characterized in that: The parameters of the flat vulcanizing press are 10 MPa, 170°C, and foaming for 6 minutes.